The applicant is studying the nature of the orienting response. Precently he is engaged in a series of studies intended both to demonstrate the inadequacy of prevailing Sokolovian OR theory, as well as to develop an alternative conception. Instead of considering the OR to be an automatic-reflexive response, dependent solely on detection of stimulus "novelty", the applicant suggested a 2- stage mechanism involving both Sokolov's matching process and a central evaluation of the potential significance of available information. Thus, he suggested a flexible OR, capable of being engaged or not when "novelty" is detected, depending on the likely value to the organism of that information. The applicant's laboratory had already begun testing this "significance hypothesis", and the present study extends these tests in several important ways: a) by examining tonic OR components as well as the more frequently studied phasic response, and b) by simultaneously studying three different response systems - heart rate, skin conductance level and eyeblink rate, thereby investigating sympathetically as well as parasympathetically mediated OR, and skeletal muscle as well as autonomic response. Data collection has been completed. While statistical analysis has not been made, visual inspection of the response curves strongly suggests support for the "significance hypothesis."